Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, implantable cardiac pacemakers and defibrillators. The devices are generally implanted in a pectoral region of the chest beneath the skin of a patient within what is known as a subcutaneous pocket. The implantable devices generally function in association with one or more electrode carrying leads which are implanted within the heart. The electrodes are usually positioned within the right side of the heart, either within the right ventricle or right atrium, or both, for making electrical contact with their respective heart chamber. Conductors within the leads and a proximal connector carried by the leads couple the electrodes to the device to enable the device to sense cardiac electrical activity and deliver the desired therapy.
Implantable cardiac defibrillators (ICD's), as well known, are capable of detecting defibrillation of the heart and delivering electrical shock therapy to one or more heart chambers to terminate the fibrillation. The defibrillating electrical energy may be applied, for example, in the superior vena cava (SVC) of the heart and/or the right ventricle (RV) of the heart. Defibrillating electrodes are generally quite large, as compared to pacing electrodes, and commonly take the form of elongated coils. The coils are usually formed of platinum which has a positive electropositivity in the blood of about +125 mV. Unfortunately, blood solids, including platelets, lymphocytes, and red blood cells all have negative charges. Therefore, they are naturally attracted to the positive charge of the platinum coils. The typical platelet has about 2 million electron charges while the white and red cells have about 10 million electron charges. Hence, in view of the forgoing, defibrillation electrodes implanted in the heart can become fibrosed to heart walls and entrapped. This may become problematic should it ever be necessary to remove such an implanted electrode due, for example, to infection or breakage.
The present invention addresses the issue of fibrosed defibrillation electrodes and other issues in connection therewith. As will be seen subsequently, the present invention reduces the likelihood of defibrillation electrode fibrosis by treating the electrodes in such a manner so as to repel fibrosis of the electrodes.